Differential wheel unit for trailers or the like



Nov. 13, 1951 MERRY 2,575,064

DIFFERENTIAL WHEEL UNIT FOR TRAILERS OR THE LIKE Filed Oct. 14, 1949 3 Sheets-Sheet 1 INVENTOR.

ATTORNEYS E. c. MERRY 2,575,064

DIFFERENTIAL WHEEL UNIT FOR TRAILERS OR THE LIKE Nov. 13, 1951 Filed Oct. 14, 1949 I5 Sheets-Sheet 2 I INVENTOR.

ATTOR N EYS E. C. MERRY Nov. 13, 1951 DIFFERENTIAL WHEEL UNIT FOR TRAILERS OR THE LIKE 5 Sheets-Sheet 3 Filed Oct. 14, 1949 INVENTOR.

ATTOR N EYs Patented Nov. 13, 1951 DIFFERENTIAL WHEEL UNIT FOR. TRAILERS 1 on THE LIKE Edward 0. Merry, Greeiisboro, N. 0., assignor of one-half to Guy M. Turner, Greensboro, N.'C.'

Application October 14, 1949, Serial No. 121,344

16 Claims. 1

This invention is a novel differential wheel unit for trailers or the like particularly adapted to be mounted on trailing vehicles to support the rear ends thereof, whereby the vehicle may be operated at normal high speeds with safety, each unit comprising a short axle carrying a relatively large single pneumatic or other wheel at each end, the axle being adapted to pivot transversely of the vehicle on an axis disposed below the axle, and the multiple units being connected together so as to cause one axle carrying member to rise or fall longitudinally of the trailer as the 'adjacent axle carrying member falls or rises, or vice versa.

The present invention is an improvement on the differential wheel unit, shown in my copending application Serial No. 61,345, filed November 22, 1948, in which the forward end of the leading longitudinal axle carrying member was positively prevented from shifting laterally with respect to the leading bracket frame while the rear end of said member was permitted a yieldable lateral shifting movement; such movement also-being permitted in the case of the forward end of the trailing longitudinal axle carrying member. The rear end of the trailing longitudinal member was permitted an unrestrained lateral movement with respect to the rear bracket frame; and both members permitted a longitudinal shifting movement with respect to the said is suspended below the axle'primarily to keep the axle itself from tipping when severe side thrusts at high speeds are encountered. In using short axles with wheels of large diameter having a center-to-center distance of approximately twentyeight inches, there would normally be a great tendency for the axles to tip laterally when the load carrying point is disposed on the axle, or adjacent to same. In order to assure that this type of unit assembly will perform satisfactorily without tipping, theload must be carried at a point sufficiently below the axle to overcome the I tipping tendency due to severe lateral tire overshifting movement, but neither member is peras possible from the ground to facilitate loading and unloading of heavy machinery, or other loads. The structures disclosed in the prior art would not be practical for fast freight carrying vehicles due to their use of dual or triple wheels at each end of the short axles, with tires having undue, sectional width. My arrangement, how: ever, is specially adapted for commercial highspeed vehicles for highway use, my unit utilizing standard sized single wheels mounted on conventional short axles instead of the usual dual or triple wheels, or special trucks, heretofore used.

Contrary to the purpose of prior art structures, in carrying the loads below the axlesfor the express purpose of maintaining the. platform height as low as possible, in my design the load loads. Research has developed the fact that if the angularity of this pivot point is located at approximately 45 or less angle from the point of wheel contact with the road, the operation of the unit is quite satisfactory and the axis is still properly positioned with respect to road clearance.

The use of large diameter tires in combination with short axles, and the location of the carrying point within the above described angular range are therefore the important features of my present invention; and the prior art structures do not specify that either such requirement is critical with respect to the 'use of short axles in'high speed highway service. Research has shown a critical relationship between the angularity of the point of road contact of the tire and the load carrying point, which angularity can range satisfactorily within the above mentioned range.

I will explain the invention with references to the accompanying drawings, which illustrate one practical" embodiment thereof, to enable others familiar with the art to adopt and use the samej and will summarize in the claims, the novel features of construction, and novel combinations of parts, for which proteotion'is desired.

In said drawings:

Figure 1 is'a side elevation, showing my novel differential 'Wheel'unit mounted to support one side of the rear end of a trailer.

Fig. 2 is a rear end view of'the differential unit shown in Fig. 1.

Fig. 3 is an enlarged horizontal section on the line 3 3, Fig. 1.

Fig. 4 is an enlarged vertical section on the line 4-4, Fig. 1.

Fig. 5 is an enlarged vertical section on the line i- 5, .Fig. 1. A

Fig. 6 is a bottom plan view of the member shown in Fig. 5.7; a

Fig. 7 is an enlarged elevation, partly in section showing the leading longitudinal axle carrying member shown in Fig. 1.

Fig. 8 is an end view of the member shown in Fig. 7.

As shown, the trailer body is provided with side frames B at each side thereof in the usual manner, same being usually of structural steel shape and sameform'ing nopart of my present invention;

My tandem wheel units are disposed at. both sides of the frame, and since the construction at both sides is identical, it is only necessary to describe the unit at one side. a

At each side of frame B adjacent the rear end thereof is an open depending frame C, consisting of opposed parallel side plates I (Figs. '1 and which are preferably outwardly flanged as at la at their upper ends and fixedly secured to the" underside of a plate 2 welded or otherwise secured to the bottom of side frame B of the trailer body by. bolts 3 or the like. The side plates I are inwardly flanged as at lb at their lower ends, and a plate 4 bridges the flanges lb, said plate having transversely elongated slots 4a therein "for the reception of bolts 5 which'pass through holes in the flanges 'Ib and through the slots 4a, same being provided with washers 6 and units ta (Fig. 5) to maintain the parallel spacing of the plates 1.

Between the bracket C and the rear end of the side frame B of the truck is a second U-shaped bracket frame D (Figs. 1 and 4) including a base "la and parallel side plates I, base Ia being secured by welding or the like to the under side of the side frame B in alignment with the bracket frame C. The side plates I are secured together at their lower ends by a plate lb welded to the lower ends thereof.

Vertically "disposed adjacent the side edges of bracket D are reinforcement plates or ribs 8 which are preferably welded to the outer faces of side plates I to strengthen the side edges thereof; and on the inner faces of side plates 1 adjacent the side edges thereof are removable wear plates 9 secured thereto by screws Ill or the like for the purpose hereinafter described. at the lower "corners of the bracket D are reinforcement plates II and at the center offthe bracket D above the plates II are reinforcement plates 12 (Fig. l) for the purpose hereinafter described, said plates 11 and I2 forming an integralportion of the bracket D.

At the rear 'end of the side frame Bis a third bracket E (Fig. 1) disposed in alignment with the brackets. Cand D, said'bra'cket E being disposed the same distance from center bracket D as the bracket C and being of identical construction, like parts being similarly numbered.

Between the bracket frames D-E is an axle T3, at each side of the rear end of the trailer, which axle is non-rotatable but carries at each end thereof ground wheels l t-J4 disposed at each side of their respective side frames B. Directly beneath each respective side frame B is an axle bracket comprising a collar I5 (Fig. "I) welded on axle l3 and having parallel depending legs I5a carrying at their lower ends a cylindrical bushing I5b adapted to snugly receive a torsilastic bushing hereinafter described, the endsof the bushing -I5b being welded to the lower ends of the legs I 5a. Straddling the legs Ilia is an inverted U -shaped strap I-B having slots Ilia at its lower end opposite bushing 15b receiving a shacklebolt I1, said shack-lebolt H extending through the slots Isa in the legs I6 and through the torsilastic bushing I5b. The lower ends of the legs of strap I6 are connected together by bolts I8 to maintain the legs I6 in spaced relation. The upper end of the inverted U-shaped strap I6 is welded in a rectangular recess I9a in a longitudinal member I9 (Fig. '7) the respective ends of which enter between the plates 1 of the center bracket D and side plates I of the bracket E, as clearly shown in Fig. 1, whereby the member I9 is maintained in longitudinal alignment with the overlying side frame members B of the trailer, the sides of member I9 directly engaging the wear plates 9 of the bracket D and the side plate I of bracket E to prevent lateral shifting of the member [9 therein, while permitting the ends of member I9 to rise and fall in brackets D and E. The rear end Illb of member I9 (Fig. 1) carries on its upper face a semi-cylindrical block I whose ends likewise contact the inner faces of the side plates I of bracket E. A leaf spring 20 has its forward end "20a secured by bolts 2| to the underside of side frame B, and its rear end 29c entered between the side plates I of bracket E, same yieldingly contacting the top of the block I90 to constantly urge same downwardly in bracket E. The forward end I9d of longitudinal member I9 is provided with spaced perforated ears I9e for the purpose hereinafter described.

Between the brackets CD is an axle I330, similar in all respects to axle I3 and carrying wheels I4 at opposite sides thereof, and a second strap I5I5a--'I5b is welded or otherwise secured to a second non-rotatable'axle I3rv same carrying at its lower end a shacklebolt II. Straddling the second strap l'5I5aI5b is a second U-shaped strap I6 similar in'all respects to the first strap I6, the base of which is welded or otherw'se secured in a correspondingly shaped recess in a second longitudinal member I9, similar in all respects to the first longitudinal member I9, said second member 16 having opposed holes in its lower end receiving the second shacklebolt 11, whereby said axle I3:c may tilt laterally with respect to the second longitudinal member I9. The forward end of the second longitudinal member I1, as shown in Figs. 1 and '7, carries a semicylindrical block I9c the ends of which contact the inner facesof the side plates I of the bracket C,s0 as to prevent lateral shifting of the forward end of the second longitudinal member I9 whilethe rear end IBd of the second longitudinal member I9 engages the wear plates 9 of the center bracket D'to likewise prevent lateral shifting of the member in bracket 'D while, however, the ends of the second longitudinal member may rise and fall in brackets C-D. The rear end of the second longitudinal member l9 within bracket D is provided with spaced perforated ears 19a for the purpose hereinafter described. A second spring 20 also bears down upon the block 19c of the second longitudinal member I9.

By the above construction, both longitudinal members l9 and their brackets, springs, and wheeled axles are identically the same, but are reversed, same having their ends "I9d adjacent and'en'ga'ged in center bracket D, and their other ends I912 engaged in brackets C and E, respec-' tively.

' In the bracket D adjacent the lower end there of is journaled'a shaft 25 (Fig. 1) on which is mounted a sprocket wheel 26; and a chain 2'! has its ends connected with the adjacent ends of both longitudinal members It utilizing the'ears I96, said chain 2'! running under sprocket 26, so

that, as the rear end of one longitudinal member rises or falls, the forward end of the other longitudinal member 19 will correspondingly fall or .rise, as the case may be.

In order to yieldably maintain the axles l3 and 13a: in the normal position shown in Fig. 1, while permitting a slight movement thereof axially of the truck body, I provide a radius rod assembly for each axle consisting of a U-shaped bracket 30 (Figs. 1 and having arcuate recesses in the outer ends of its legs receiving the side of the axle to which the bracket 30 is welded. Between the side plates I and the reinforcing plates ll of center bracket D is a bolt 3| on which is a rubber bushing 32 surrounded by a cast steel ring 33 connected with one end of a rod 34 the outer end .of

which passes through a hole in the base of bracket .30, said rod 34 being threaded and carrying nuts 35 at each side of the base of the bracket 30, also lock nuts 36, said nuts permitting adjustment of the length of the radius rod assembly. Rubber bushing 32 also permits the radius rod to shift slightly in the longitudinal direction of the rod. As shown in Fig. 1, one rod assembly 30-36 would normally be under compression and the other under tension while the truck is moving, but by reversing one assembly both rods could be arranged to operate under tension or compression, the changed rod being secured to a bracket C or -E instead of the center bracket D. The above construction provides a trailer wheel unit at each side of the rear end thereof which will be practical for fast freight carrying vehicles involving the use of single wheels on short axles equipped with ordinary tires thereon of ordinary size for fast highway operation.

In my design, the load of the trailer is carried at points below the axles, in order to keep the axles l3 and l3a: from tipping when severe speed thrusts are introduced. Ordinarily, in using short axles with large diameter wheels there is a strong tipping tendency but for fast freight the load must be carried at, a point sufficiently below the axle 'to' overcome the tipping tendency under severe tire overloads. I have found that in order to maintain the axle stability, the load carrying point must be enough below the axle so that the angularity of a line X (Fig. 2) drawn from the center of the tire of a related wheel Id at the point of road contact to the axle pivoting point I! must be 45 or less, and my entire arrangement is designed accordingly. Thus, when the trailer is being drawn at high speeds there is little or no tendency on the part of the axles l3 and I31: to tip, and therefore maximum axle stability is maintained.

I do not limit my invention to the exact form shown in the drawings for obviously changes may be made therein within the scope of the claims.

I claim:

1. In a trailer having a body; forward end, intermediate, andrear end spaced aligned openended bracket frames depending below the body;

horizontal aligned members having their ends' entered into and slidably contacting the walls of adjacent pairs of bracket frames for preventing transverse movement of the members therein while permitting vertical movement therein; relatively short axles carried by said members and mounted to pivot transversely thereof, the pivot points being intermediate the ends of and disposed below said axles; wheels journaled on the respective ends of said axles; means in the intermediate bracket frame connecting the adjaend of one member rises the end of the other said yieldable means comprising springs having one of their ends secured to the body and their other endsentering the end brackets and contacting the ends of said horizontal members 3. In a trailer as set forth in claim 1, said members having inverted U-shaped portions straddling the axles; other inverted U-shaped membersjournaled on the axles and embraced by the first named U-shaped members; and bushings transfixing the lower overlapping ends of the U-shaped members and forming the said pivot points of the axles.

, 4. In a trailer as set forth in claim 3, the angularity of the pivot points with respect to the central points of contact of a related wheel with the road surface being no greater than 45, in order to minimize tipping tendency of the axles at high trailer speeds when the body is subjected to substantial lateral thrusts.

5. In a trailer as set forth in claim 1, brackets secured to the axles to which one of the ends of the rods are adjustably connected, said rods having bearing rings at their other ends disposed within a bracket frame; and bushings passing through said rings and having their ends mounted in the said bracket.

6. In a trailer having a body provided with side beams; forward end, intermediate, and rear end spaced aligned open-ended bracket frames depending below the side beams; horizontal aligned members having their ends entered into and slidably contacting the walls of adjacent pairs of bracket frames for preventing transverse movement of the members therein while permittin vertical movement therein; relatively short axles carried by said members and mounted to pivot transversely thereof, the pivot points being intermediate the ends of and disposed below said axles; single wheels journaled on the respective ends of said axles; means in the intermediate bracket frame connecting the adjacent ends of the said members whereby as the end of one member rises the end of the other member will correspondingly fall, and vice versa; rods mounted for yieldable longitudinal movement on the bracket frames and secured to the respective axles; and means yieldably urging the outer ends of the horizontal members downwardly in their respective brackets.

7. In a trailer as set forth in claim 6, said brackets including spaced parallel-side plates engaging the sides of the horizontal members; semi-cylindrical projections on the tops of the outer ends of the horizontal members within the end brackets; and said yieldable means comprising leaf springs having one of their ends secured to the side beams and their other ends entering the end brackets and contacting the said projections.

8. In a trailer as set forth in claim 6, said members having inverted U-shaped portions straddling the axles; other inverted U-shaped members journaled on the axles and embraced by the first cent ends of the said members whereby as the named p members; and rubber torque amt 7 bushings transfixing thelower overlapping ends of the U-shaped members and forming the said pivotpoints ofthe axles.

9. In a trailer as setforthin claim & the aneularity of the pivotpoints with respect tothe centralpoints of contact of a related wheel with the road surface being no greater than 45 in order to minimize tipping tendency of the axlesat high trailer speeds when the body is --su-bjected to substantial lateral'thrusts. V

.10. In a trailer as set forth in ,claimfi, U -shaped brackets secured to theaxles to which one of the ends of the rods are adjustably connected, said rodshaving bearing rings at their other endsdisposed within a bracket frame; and rubber torque bushings passing through-said rings and having their ends mounted in the said bracket.

11. in a trailer having a body vprovided with side beams; for-ward end, intermediate, andrear end spaced aligned open-ended bracketframes depending below the side beams; horizontal aligned members having their ends entered into and slidably contacting the-walls of adjacent pairs of bracket frames for preventing transverse movement of the members therein while. permitting vertical movement therein; relatively short axles carried by said members and mounted to pivot transversely thereof, the pivot points being intermediate theends of and disposed below said axles;

single wheels journaled on the respective ends of said axles; means in theintermediate bracket frame connecting the adjacent ends of the said members whereby as the end of one memberrises the end of the other member will correspondingly .fall, and vice versa; rods mounted tor yieldable longitudinal movement on the intermediate bracket frame and secured to the respective axles; andmeans yieldably urging "the outer ends of the horizontal members downwardly in their respective brackets.

12. .In a trailer as set forth in claim 11, said brackets including spaced parallel side plates'engaging thesides-of the horizontal members; :semicylindrical projections on the tops of the outer ends of the horizontal members within the end '8 brackets", and said yieldable means comprising leaf springs having one of their-ends secured to fthe side beams and their other ends entering the end brackets and contacting the said projections.

13. .In .a trailer as set forthin claim 11, said :members having inverted U-shaped portions straddling the axles; other inverted U-shaped members :journaledon the axles and embraced by the first named U -shaped members; andrubber torque bushings transfixing the lower overlapping "ends of the U-shaped members and forming the saidpivotpoints'of'theaxles.

14. In a trailer as set forth in claim '13, the angnlarity of the pivot points with respect to the central points of contact of a related wheel with the road surface being no greater than 45" in order to minlmize tipping tendency ofithe axles at high trailerspeeds when the body-issubiected to substantial lateral thrusts.

15. In a trailer as set forth in claim 11, said connecting means comprising a sprocket wheel journaled'in the intermediate bracket frameyand a .chain running under the sprocket and-having'its ends respectively connected with the adjacent ends of saidmenfoers.

16. In a trailer as set forth in claim 11, U- .shaped brackets secured to the axles-to'whiohone of the ends of the are adj ustahly connected, said rods having rings at their other ends disposed within the intermediate oracket frame; and rubber torque bushings passing throughsaid rings and having their ends mounted in the said bracket.

EDWARD C. MERRY.

REFERENCES @ITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,928,860 'Marcum Got. :3, 1933 2,411,690 Keller, Jr Mar. 18,1947 14%,205 Wickersham et a1. Aug. :3, 1948 

